Transport of hydrophobic pollutants in rivers such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals is often facilitated by suspended sediment particles, which are typically mobilized during high discharge events. Suspended sediments thus represent a means of transport for particle related pollutants within river reaches and may represent a suitable proxy for average pollutant concentrations estimation in a river reach or catchment. In this study, multiple high discharge/turbidity events were sampled at high temporal resolution in the Globaqua River Basins Sava (Slovenia, Serbia), Adige (Italy), and Evrotas (Greece) and analysed for persistent organic pollutants such as PAHs (polycyclic aromatic hydrocarbons) or PCBs (polychlorinated biphenyls) and heavy metals. For comparison, river bed sediment samples were analysed as well. Further, results are compared to previous studies in contrasting catchments in Germany, Iran, Spain, and beyond. Overall results show that loadings of suspended sediments with pollutants are catchment-specific and relatively stable over time at a given location. For PAHs, loadings on suspended particles mainly correlate to urban pressures (potentially diluted by sediment mass fluxes) in the rivers, whereas metal concentrations mainly display a geogenic origin. By cross-comparison with known urban pressure/sediment yield relationships (e.g. for PAHs) or soil background values (for metals) anthropogenic impact - e.g. caused by industrial activities - may be identified. Sampling of suspended sediments gives much more reliable results compared to sediment grab samples which typically show a more heterogeneous contaminant distribution. Based on mean annual suspended sediment concentrations and distribution coefficients of pollutants the fraction of particle facilitated transport versus dissolved fluxes can be calculated.
Keywords:Knudsen effusion mass spectrometry Redlich-Kister-Muggianu model Activity Excess Gibbs energy Ternary and binary L-parameter a b s t r a c tThe vaporisation of a liquid Al-Cu-Sn system has been investigated at 1273-1473 K by Knudsen effusion mass spectrometry (KEMS) and the data fitted to a Redlich-Kister-Muggianu (RKM) sub-regular solution model. Thirty-one different compositions (41 samples) have been examined at eight fixed copper mole fractions, X Cu = 0.10, 0.20, 0.30, 0.333, 0.40, 0.50, 0.60 and 0.70. The ternary L-parameters, the thermodynamic activities and the thermodynamic functions of mixing have been evaluated using standard KEMS procedures. In addition, the same quantities were obtained from the measured ion intensity ratios of Al + to Cu + , Al + to Sn + and Cu + to Sn + using a mathematical regression technique. The intermediate data obtained directly are the RKM ternary L-parameters that are, as a function of temperature, as follows:(0) = (14270 ± 1270) + (100.1 ± 7.6)T − (11.77 ± 0.93)T ln(T ); L (1) = (145600 ± 9780) + (101.6 ± 58.7)T − (15.56 ± 7.14)T ln(T ); L (2) = (76730 ± 1240) + (79.2 ± 7.4)T − (15.69 ± 0.91)T ln(T ).From the obtained ternary L-parameters the integral molar excess Gibbs energy, the excess chemical potentials, the activity coefficients and the activities have been evaluated. Using the temperature dependence of the activities, the integral and partial molar excess enthalpies and entropies can be also determined. In addition, for comparison, for some compositions, the Knudsen effusion isothermal evaporation method (IEM) and the Gibbs-Duhem ion intensity ratio method (GD-IIR) were used to determine activities and good agreement was obtained from the RKM model.
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